Method for depositing metal and metal oxide films and patterned films

ABSTRACT

The invention is directed to a photoresist-free method for depositing films composed of metals, such as copper, or its oxides from metal complexes. More specifically, the method involves applying an amorphous film of a metal complex to a substrate. The metal complexes have the formula M f L g X h , wherein M is selected from the group consisting of Ti, V, Cr, Au, Mn, Fe, Co, Ni, Cu, Zn, Si, Sn, Li, Na, K, Ba, Sr, Mo, Ru, Pd, Pt, Re, Ir, and Os, L is a ligand of the formula (R 2 NCR 2 ′CO) wherein R and R′ are independently selected from H, C n H m  and C n H m A x B y  wherein A and B are independently selected from main group elements and f, g, h, n, m, x and y represent integers and wherein X is an anion independently selected from N 3 , NCO, NO 3 , NO 2 , Cl, Br, I, CN, OH, H and CH 3 . These films, upon, for example, thermal, photochemical or electron beam irradiation may be converted to the metal or its oxides. By using either directed light or electron beams, this may lead to a patterned metal or metal oxide film in a single step.

FIELD OF THE INVENTION

This invention relates to the use of metal complexes to deposit films ofmetals or metal oxides. Such films may be of use in a variety ofapplications, including but not limited to microelectronics fabrication.

BACKGROUND OF THE INVENTION

Deposition of thin films using non-vacuum techniques normally compriseseither sol gel or metal organic materials or comprises photochemicalmetal organic depositions. Films of inorganic materials are usuallydeposited by chemical or physical vapor deposition, although in somecases, sol gel or metal organic deposition has been used. The sol gel ormetal organic depositions require the construction of films ofprecursors. These films are then heated to drive off the organiccomponent, leaving a metal or more commonly, a metal oxide film. Thephotochemical deposition method differs from the above two methods inthat the reaction which drives off the organic component isphotochemically activated. Since none of these methods are able to formthe patterned structures normally used in the construction ofmicroelectronic devices or circuits, they must be employed with otherprocesses in order to pattern films of materials.

Hybrid methods often use light as the energy source wherein the lightused initiates a thermal rather than a photochemical reaction. Thesemethods have the disadvantage that they do not directly result in theformation of patterned films but result in the unselective deposition ofthe films.

Additional disadvantages of the previously described deposition methodsare that they require the use of expensive equipment and many of themrequire high temperature processing.

Because of the problems associated with possible contamination of cleanroom facilities, a single chemical which may be used for differentdeposition methods is desirable. Furthermore, the use of a singlechemical for different deposition methods reduces the productdevelopment expense to the supplier.

Metals, such as copper, may be used as a conductor in electroniccircuits. Other metal oxides, such as copper oxide, are semiconductorsand have found use as a conductor in electronic circuitry. Accordinglythere is much interest in developing methods of achieving the depositionof metals and the patterned deposition of metals or their oxides onvarious substrates.

U.S. Pat. No. 5,534,312 to Hill et al., incorporated herein byreference, describes a method for the deposition of a variety of metaland metal oxide systems using photochemical deposition. It will beappreciated that the approach discussed therein is a substantialimprovement in the prior art. The current invention presents new typesof metal complexes or precursors which are useful for thermal, electronbeam, and photochemical patterning of copper containing materials and amethod for depositing these complexes.

Prior art precursors used to deposit metal or metal oxide films, such asthat shown below, and disclosed in U.S. Pat. No.5,534,312, are known tofragment under photolytic conditions, leading to the loss of CO₂. Thisfragmentation leaves the metal atoms unbound.

Complexes disclosed by Chung et al. in J. Chem. Soc., Dalton Trans.,1997, p. 2825-29, which is incorporated herein by reference, alsocomprise a pair of metal atoms bonded to bidentate organic ligands. Themost general form of these complexes has the following formula.

In the above formula, the individual sites where substitution may beused to optimize the physical and chemical properties are shown. Theorganic ligand framework of these complexes shows no obvious site forfragmentation under, for example, photolytic conditions. Therefore, itis not clear that complexes of this formula should be suitable forphotolytic deposition of metals or metal oxides. In fact it couldreasonably be predicted that the photochemical reactivity should centerabout the groups X₁ and X₂ in the figure. Indeed, the publishedphotochemistry for this complex (Chung et al., (1997) J. Chem. Soc.Dalton Trans., 2825) leads one of skill in the art to expect thatphotochemistry should yield a stable Cu(I) complex. Based on the priorart, one would not expect it to be possible to use these new precursorsto deposit metal or metal oxide films at all. In an amorphous filmcomprising such a complex, however this is not the case and Cu metal isformed, a highly unexpected result.

It is therefore surprising that new precursors of the form shown abovehave been found that are useful in depositing films composed of a metal,such as copper, or its oxides. These new precursors exhibit anunexpected fragmentation site to yield the desired metal or metal oxidefilm. Preliminary mass spectral evidence suggests that the ligand infact degrades during the photoreaction, a result that was not readilypredicted.

SUMMARY OF THE INVENTION

The present invention is directed to a photoresist-free method fordepositing films composed of a metal, such as copper, or its oxides frommetal complexes. More specifically, the method involves applying anamorphous film of a metal complex to a substrate. The complexes of thepresent invention are generally of the formula, M_(f)L_(g)X_(h), whereinM is selected from the group consisting of Ti, V, Cr, Au, Mn, Fe, Co,Ni, Cu, Zn, Si, Sn, Li, Na, K, Ba, Sr, Mo, Ru, Pd, Pt, Re, Ir, and Os, Lis a ligand of the formula (R₂NCR₂′CO) wherein R and R′ areindependently selected from H, C_(n)H_(m) and C_(n)H_(m)A_(x)B_(y)wherein A and B are independently selected from main group elements andf, g, h, n, m, x and y represent integers, and X is an anionindependently selected from N₃, NCO, NO₃, NO₂, Cl, Br, I, CN, OH, H,CH₃. In a preferred embodiment, the metal is dinuclear copper, theligand is 1-diethylaminoethan-2-ol, and the anion is selected from N₃,NCO, and NO₂.

These films, upon either thermal, photochemical or electron beamstimulus may be converted to a metal or its oxides. By using eitherdirected light or electron beams, this may lead to a patterned metal ormetal oxide film in a single step. The metal (e.g., copper) or its oxide(e.g., copper oxide) deposited by this method is conductive.Accordingly, these metal precursors and the deposition of the metals ortheir oxides from such precursors is a useful invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The current invention describes the use of complexes of metals such ascopper, to form films which may be activated by thermolysis, chargedparticles (such as electron beams), or photons to deposit coppercontaining films.

An amorphous precursor film comprising the complex is deposited onto asubstrate using methods well known in the art, such as spin or dipdeposition. This film is then exposed to electromagnetic radiation orelectron or ion beams. This exposure results in the conversion of theexposed areas from the precursor material to the desired amorphous filmof the metallic material. The precursor complexes of the presentinvention are generally of the formula, M_(f)L_(g)X_(h), wherein M isselected from the group consisting of Ti, V, Cr, Au, Mn, Fe, Co, Ni, Cu,Zn, Si, Sn, Li, Na, K, Ba, Sr, Mo, Ru, Pd, Pt, Re, Ir, and Os, L is aligand of the formula (R₂NCR₂′CO) wherein R and R′ are independentlyselected from H, C_(n)H_(m) and C_(n)H_(m)A_(x)B_(y) wherein A and B areindependently selected from main group elements and f, g, h, n, m, x andy represent integers, and X is an anion independently selected from N₃,NCO, NO₃, NO₂, Cl, Br, I, CN, OH, H, CH₃.

An example of such precursor complexes include dinuclear coppercomplexes with suitable bidentate ligands. Suitable ligands include:μ-aminopropan-2-olate, diethylaminoethan-2-olate,diethylaminobutan-2-olate, and the like. Related complexes are disclosedby Chung et al. in J. Chem. Soc., Dalton Trans., 1997, p. 2825-29. Suchdinuclear copper precursor complexes are generally of the formula:Cu₂(μ-R₂NCR′CO)₂(X)₂, wherein R and R′ are independently selected fromH, C_(n)H_(m) and C_(n) H_(m) A_(x) B_(y) wherein A and B areindependently selected from main group elements and n, m, x and yrepresent integers, and X is an anion independently selected from N₃,NCO, NO₃, NO₂, Cl, Br, I, CN, OH, H, and CH₃.

Although dinuclear copper complexes with bidentate ligands areexemplified in the present disclosure, the present invention is notlimited to copper complexes. Other suitable metals that can be used inthe present invention include: Ti, V, Cr, Au, Mn, Fe, Co, Ni, Cu, Zn,Si, Sn, Li, Na, K, Ba, Sr, Mo, Ru, Pd, Pt, Re, Ir, Os and similarmetals. One skilled in the art could determine the correspondingstoichiometry for the particular metal and the general ligandformulations provided above.

Presently, preferred metal complexes include Cu₂(μ-Et₂NCH₂CH₂O)₂(N₃)₂,Cu₂(μ-Et₂NCH₂CH₂O)₂(NCO)₂, and Cu₂(μ-Et₂NCH₂CH₂O)₂(NO₂)₂.

Typical films may be deposited on various substrates. These includematerials as wide ranging as simple salts, such as CaF₂, tosemiconductor surfaces such as silicon. The nature of the substrate isnot critical for the process although it may affect the method ofdeposition of the precursor film and the solvent for the deposition, ifone is used. Applicable solvents include acetone, dimethylsulfoxide,dimethylacetamide, 2-methoxyethanol and the like. The most commonly usedsubstrate has been silicon but is not limited thereto. These siliconsubstrates may have been coated with other layers such as dielectriclayers, photoresist or polyimide, metal oxides, thermal oxides,conduction materials, insulating materials, ferroelectric materials, orother materials used in the construction of electronic devices. Theseinclude single crystal wafers.

The precursor film may be deposited on the surface by spin coating themolecule from a solvent. In this procedure, the precursor is dissolvedin a solvent to form a precursor solution. The substrate surface is thenput on a surface which can be spun. The substrate may be held in placewith a vacuum chuck, such as present in a commercial spin coater (e.g.,from Headway or Laurell Corporation). The precursor solution isdispensed onto the surface of the substrate either before commencingspinning or while the substrate is spinning. The substrate is thenallowed to spin, resulting in the deposition of a thin film of theprecursor on the surface.

The film thickness obtained in this process can be varied by varyingboth the spin rate and the concentration of the precursor in thesolvent. To obtain a suitable film, the spin speed may be changed duringthe spinning process.

The films may also be formed by other methods known to those skilled inthe art, including, but not limited to, spray on coating, dip coating,and various inking methods. Additives may be included, for example, toimprove the quality of the resultant film by preventing cracking or toenhance another film property. Examples of such additives include, butare not limited to, monoethanolamine and diethanolamine. One skilled inthe art could determine other suitable additives to suit the particularpurpose.

The film is then exposed to a source of irradiation. Typically, the filmmay be exposed to light directed through an optical mask used to definea pattern on the surface. The mask consists of transparent and lightabsorbing regions. The mask may also include an optical enhancingfeature such as a phase shift technology. Exposure of the film with thislight results in a chemical reaction within the film which changes thefilm from precursor to the product.

The light does not necessarily have to be directed through a mask. Forexample, if it is not necessary to pattern the material, a floodexposure may be used. Alternatively, if patterning is desired, a directwriting approach may be used. In a common implementation of the directwriting process, a laser beam is directed in a serial fashion over thesurface, resulting in exposure only of the areas where the beam wasdirected. Alternatively, near field optical systems allow selectiveexposure of some areas of the surface.

Normally, the atmosphere used for the exposure is air. It may, for avariety of reasons, be preferable to change the composition of theatmosphere present during exposure. One reason is to increase thetransmission of the exposing light, if short wavelength light is used,because it may be attenuated by air. It may also be desirable to changethe composition of the atmosphere to alter the composition or propertiesof the product film. For example, in air or oxygen, the exposure of acopper complex results in the formation of a copper oxide. By changingthe humidity of the atmosphere, the amount of water in the film may bechanged. By eliminating oxygen entirely from the atmosphere, a filmconsisting primarily of copper may be formed. By increasing theintensity of the light, it is possible to initiate a thermal reactionwithin the films to generate product films.

Exposure may also be carried out with ion or electron beams. These arenormally directed in a serial write process. The ion or electron beam isdirected onto the precursor film, causing a reaction to produce theproduct film in the exposed areas. The nature of the exposure systemsfor ion and electron beams is such that these are normally done within avacuum. The deposit from such a process may, depending upon theconditions, be the metal which upon exposure to air is oxidized to formthe oxide.

Thermal energy may also be used to convert the precursor films to copperbased films. This may find specific use if some areas are patterned toform copper layers, then in a thermal reaction the remaining material isconverted to copper oxide by thermolysis in air. Alternatively, thecopper regions may be photo-patterned and the remaining areas mayundergo unselective thermal reaction. It should be noted, however, thatsome oxidation of the deposited copper may occur and this film may bethe preferred use of this process.

EXAMPLE 1

In a preferred embodiment, a precursor Cu₂(μ-Et₂NCH₂CH₂O)₂(N₃)₂ wasdeposited on a substrate. The Cu₂(μ-Et₂NCH₂CH₂O)₂(N₃)₂ film was thenphotolyzed with ultraviolet light (254 nm) in a nitrogen atmosphere. Theprogress of the reaction was monitored by Fourier transform infraredspectroscopy. Following exhaustive photolysis, the conductivity of thefilm was measured. The films were found to have a conductivity of 1.8μΩcm. The films were examined and found to consist of copper.

Alternatively, a similar precursor film exposed in air resulted in theformation of copper oxide. This oxide film could be reduced by hydrogenor any other suitable reductant at elevated temperatures to yield copperfilms.

EXAMPLE 2

In another preferred embodiment, a mixture of two precursors composed ofboth Cu₂(μ-Et₂NCH₂CH₂O)₂(N₃)₂ and Cu₂(μ-Et₂NCH₂CH₂O)₂(NCO)₂ wasdeposited to form a film. This film was photolyzed to form a conductivecopper based film.

EXAMPLE 3

In another embodiment, a film of Cu₂(μ-Et₂NCH₂CH₂O)₂(N₃)₂ was depositedand photolyzed through a lithography mask. The resultant film was rinsedwith ethylacetate and a copper oxide pattern remained on the surface.

EXAMPLE 4

In another embodiment, the metal complexes were mixed with an additionalchemical agent to lessen the effect of shrinkage. Such agents may insome cases act by preventing the ordering which results in thestructured layered films. One example of such an agent which has beentested is diethanolamine. The lithographic deposition of the metalcomplexes then occurs with improved image replication.

EXAMPLE 5

In another embodiment, a mixture of Cu₂(μ-Et₂NCH₂CH₂O)₂(N₃)₂ andUO₂(O₂CC₅H₁₁)₂ was cast as a thin film. This material was photolyzed,leading to a film whose complex was that of a copper uranium oxide.

Those skilled in the art will appreciate that variations to theabove-described methodology may occur without departing from the scopeof the invention.

What is claimed is:
 1. A method for producing a patterned film of a metal containing material on a substrate comprising: a) depositing an amorphous film of a metal precursor complex of the formula: M_(f)L_(g)X_(h), wherein M is selected from the group consisting of Ti, V, Cr, Au, Mn, Fe, Co, Ni, Cu, Zn, Si, Sn, Li, Na, K, Ba, Sr, Mo, Ru, Pd, Pt, Re, Ir, and Os, L is a ligand of the formula (R₂NCR₂′CO) wherein R and R′ are independently selected from H, C_(n)H_(m) and C_(n)H_(m)A_(x)B_(y) wherein A and B are independently selected from main group elements and f, g, h, n, m, x and y represent integers and wherein X is an anion independently selected from N₃, NCO, NO₃, NO₂, Cl, Br, I, CN, OH, H and CH₃; and b) irradiating said amorphous film to cause said metal complex to undergo a reaction which transforms said metal complex into a metal containing material adherent to said substrate.
 2. The method of claim 1 wherein said irradiating is accomplished by directing laser beam.
 3. The method of claim 1 wherein said irradiating is accomplished by heating.
 4. The method of claim 1 wherein said irradiating is accomplished utilizing an electron beam.
 5. The method of claim 1 wherein said irradiating is accomplished utilizing an ion beam.
 6. The method of claim 1 wherein said irradiating is accomplished utilizing a source of visible light.
 7. The method of claim 1 wherein said irradiating is accomplished utilizing a source of ultraviolet light.
 8. The method of claim 1 additionally comprising the step of reducing said metal containing material after said irradiating step.
 9. The method of claim 1 wherein said irradiating step is carried out in a vacuum.
 10. The method of claim 1 wherein said irradiating step is carried out in a controlled atmosphere.
 11. The method of claim 10 wherein said controlled atmosphere is air.
 12. The method of claim 10 wherein said controlled atmosphere is nitrogen.
 13. The method of claim 1 additionally comprising the step of covering said amorphous film with a mask that leaves said patterned area exposed.
 14. The method of claim 1 wherein the resulting film is a metal oxide.
 15. The method of claim 1 wherein said metal, M, contains Cu.
 16. The method of claim 1 wherein said metal is a dinuclear copper.
 17. The method of claim 1 wherein said anion is N₃.
 18. The method of claim 1 wherein said group R is Ethyl.
 19. The method of claim 1 wherein said substrate is silicon.
 20. The method of claim 1 wherein said substrate is CaF₂.
 21. A method for producing a copper containing film on a substrate comprising: a) depositing an amorphous film of a dinuclear copper complex of the formula Cu₂(μ-R₂NCR₂′COO)₂(X)₂ wherein R and R′ are independently selected from the group consisting of H, C_(n)H_(m) and C_(n)H_(m)A_(x)B_(y) wherein A and B are independently selected from main group elements and n, m, x and y represent integers, wherein X is an anion selected from the group consisting of N₃, NCO, NO₂; and b) irradiating said film to cause said metal complex to undergo a reaction which transforms said copper complex into a copper containing material adherent to said substrate.
 22. The method of claim 1 wherein additives have been added to the metal precursor complex to improve the quality of the resultant film.
 23. The method of claim 1 wherein the film contains one or more metal complexes in addition to said metal complex.
 24. The method of claim 1 wherein an additive is used to improve the film forming quality.
 25. The method of claim 1 wherein the metal is a transition metal.
 26. The method of claim 1 wherein said irradiating is carried out by photolysis. 